Computer systems typically comprise a combination of computer programs and hardware, such as semiconductors, transistors, chips, and circuit boards. The computer programs are stored in the storage devices and are executed by the processors.
One use of computers is for the implementation of virtual machines, which execute on a physical machine. A virtual machine (VM) is a program implementation of a physical machine that executes programs. Virtual machines allow the sharing of physical machine resources between different virtual machines, each running its own operating system (typically called guest operating systems), which may be the same or different from each other. Virtual machines may allow multiple operating system environments to co-exist on the same computer, in isolation from each other. Virtual machines may provide an instruction set architecture that is somewhat different from that of the underlying physical machine.